Here is a couple of trusses I designed using a generic model family creator. Feel free to use and modify as needed.
a couple of tips-
-to make the extrusions parametric with the reference lines, first click into the extrusion editor AND THEN align& lock the extrusion lines with the reference lines. If you try to align the extrusions to the reference lines before going into the extrusion editor it will not work.
-Make the whole truss as a single extrusion.- I attempted to make the heel, bottom chord and top chords as individual members which created problems.
-The dimensions I give are parametric, so you will be able to adjust them inside the properties box within the project.
4/12 slope= 18.43deg.
3/12 slope= 14.04deg.

-if you want to make more parametric constraints, use the dimension tool to align with the reference lines, NOT the extrusion pieces. After setting the dimension notation, then go into the extrusion editor and align & lock the extrusion to the reference line. If you try to snap the dimension to the extrusion, it will not work.

Parametric Truss W-overhang.rfaParametric Truss W- single slope.rfa